Have you had a look at the backside of the belt?
Belt faults are sometimes caused by a seized tension pulley or a broken water pump.
So maybe you should check both.
The tension pulley has a roller (two) bearing inside which can be replaced.
I think beside this the tension mechanic is a reliable part.
As long as nobody has replaced the spring or mounted the washers in a wrong way.
The water pump should be turned by hand in a smooth way. No heavy friction and no slack.
At the moment it looks like most of teh Gileristi here are watching adult men in shorts, running around on a gras field, hunting a little ball
So maybe the 'real specialists' will answer later.